Half-burned diesel particulate is absolutely cancerous, it can enter the bloodstream and cross the blood-brain barrier and they're generating clouds of it, probably thousands of times more than what a modern 18 wheeler puts out in half an hour of driving. And they're doing it to someone breathing hard.
If I sprayed some cancerous chemical in someone's face, I'd be arrested within the hour. I'd be on the regional news, even.
The double standards around motor vehicles never cease to amaze.
I had no idea this was a thing, much less that it was something people did on purpose.
In terms of US cultural exports, for every jazz music and snowboarding I guess there has to be some coal rolling and fake service dogs.